Research On Qos Guarantee Methods In Satellite Internet

Currently, Internet is confronted with a series of intractable problems, including backbone congestion, difficult access, slow content delivery, etc. As a significant component of air-space-ground integrated information network in the future, satellite Internet, which has advantages of global coverage, remote access and broadcasting, is an effective solution to above problems. For the purpose of providing ubiquitous communication and information services, satellite network is becoming satellite Internet with high effectiveness. However, there are some technical challenges in designing and realizing satellite Internet. Quality of service (QoS) is the primary problem in these challenges. On one hand, the IP QoS challenges in ground Internet will still exist in satellite Internet. On the other hand, due to inherent characteristics of satellite communication, the QoS issue in satellite Internet has some particularity.Therefore, analyzing QoS requirements and designing efficient and easily implemented QoS guarantee algorithms are crucial points in satellite Internet. At present, most of researches on QoS guarantee in satellite Internet concentrate on controlling congestion and suitability of TCP over satellite links. On one hand, TCP congestion control scheme is based on end-to-end not knowing about internal status in networks. On the other hand, various methods based on TCP layer still cannot completely adapt to satellite links due to the feedback mechanism of TCP. In addition, resource allocation in satellite networks is more complex than ground networks due to handoff and mobility. From the perspective of network traffic, focusing on solving network congestion in network (IP) layer and enhancing resource allocation, this dissertation studies QoS guarantee methods in satellite Internet in-depth by referring to the latest researches. Not only does it perfect the QoS guarantee system of satellite Internet, but also have referential significance for QoS guarantee of the future air-space-ground integrated information network. Aiming at key QoS guarantee algorithms in satellite Internet, the dissertation deals with the following aspects:Firstly, investigation in traffic self-similarity in satellite networks. There are many researches on the effect of self-similarity on QoS of terrestrial networks, but there is little work on traffic self-similarity and its effect of satellite networks. In view of the situation, aggregation and propagation properties of self-similar traffic in satellite networks is analyzed considering characteristics of satellite networks. Then, by building a ground gateway model, the propagation property of self-similar traffic is analyzed and simulated when the traffic from wired ground networks is released to wireless satellite links through the gateway. In addition, the effect of self-similarity on node queue performance is simulated and analyzed for the purpose of presenting algorithms to improve QoS.Secondly, research on self-similar traffic prediction. In the light of the negative effect of ubiquitous self-similarity in satellite Internet traffic on network performances and the predictability in self-similar traffic, an improved Kalman filtering algorithm for predicting self-similar traffic is proposed. As classical Kalman filtering method cannot solve the proposed filtering model, a new filtering process is deduced. In addition, on-line noise estimation is introduced to enhance precision. The algorithm is highly accurate with the correlation structure similar to the real traffic trace.Thirdly, study on active queue management (AQM) based on traffic prediction. AQM is a method of controlling congestion in IP layer, while traffic prediction is significant for AQM. Considering low efficiency of existing AQM algorithms in congestion estimation, an AQM algorithm combined with adaptive traffic prediction is presented. The algorithm estimates congestion using the above improved Kalman filtering. Packet dropping decision is made based on the predicted results and a measurement-based packet loss ratio. It dynamically adjusts packet dropping probability, with advantages of stable queue and high link utilization.Fourthly, work on fair QoS bandwidth allocation algorithm in satellite networks. Excessive reservation and deficient fairness are major drawbacks in existing bandwidth allocation algorithms of satellite networks. According to these flaws, a new bandwidth allocation algorithm based on fair QoS is presented. As the algorithm introduces adaptive bandwidth reservation strategy and fair utility bandwidth allocation rule, it maintains effectiveness of user's connection, while guarantees fairness of QoS among multiple users.